1. Field of the Invention
The present invention relates to a CAD-system (Computer Aided Design system) projection method for adding dimension lines for two-dimensional elements in a two-dimensional space obtained by performing projection processing on a three-dimensional model including three-dimensional elements, a CAD system, and a recoding medium for executing the method in an appropriate system capable of reading information stored in the recoding medium.
2. Description of the Related Art
In order to add dimension lines to a two-dimensional drawing in a CAD system, a two-dimensional drawing is created from a three-dimensional model through projection processing and a user uses a tool (a dimension-line tool) for drawing dimension lines in the two-dimensional space of the two-dimensional drawing to specify the starts and ends of the dimension lines. Thus, every time the user modifies the three-dimensional model and obtains a two-dimensional drawing that includes the reflected modification through projection processing, he or she needs to modify the dimension lines as well. The modification must be made on each drawing, and thus, the load of the user is considerable.
In response, there is a CAD system that adds dimension lines to a three-dimensional model and that automatically adds dimension lines that are to be subjected to projection processing during projection processing to a two-dimensional drawing. According to the system, when the user modifies an assembly, component, or the like in a three-dimensional mode, he or she modifies dimension lines as well. This eliminates a need for modifying each drawing, at least, in the two-dimensional space of the two-dimensional drawing, thus resulting in an improvement in the user's work.
However, even the background technology has problems as follows. The problems will be described with reference to drawings.
Suppose an assembly drawing shown in FIG. 11 is created when an assembly including a component M1, a component M2, and a component M3 shown in FIG. 10 is designed. FIG. 11 is an assembly drawing obtained by performing projection processing on the components included in the assembly shown in FIG. 10, except for the component M2. When such an assembly drawing is to be created, a user specifies the component M1 and the component M3 or specifies exclusion of the component M2 during projection processing to perform projection processing. After creating the projection drawing shown in FIG. 11, the user adds dimension lines to a three-dimensional model, as shown in FIG. 12, by using a scale-line tool. When the user specifies the projection drawing shown in FIG. 11 and gives an instruction for projection processing, a projection drawing shown in FIG. 13 to which all dimension lines to be projected are added based on a projection direction of the three dimensional model shown in FIG. 12 is created. However, when the projection drawing shown in FIG. 11 is created, a dimension line for the component M2 excluded from objects to be projected (i.e., a dimension line corresponding to a circled dimension line in FIG. 13 and to a circled dimension line in the three dimensional model in FIG. 12) is also inserted into the projection drawing shown in FIG. 13, and this dimension line is an unnecessary line that is different from the user's intension. Thus, since all dimension lines that are added to the three-dimensional model and that are to be projected are added to the projection drawing based on the projection direction, there is a problem in that an unnecessary dimension line is added. In the above-described case, for convenience of description, one component is excluded from objects to be projected. However, during creation of an assembly drawing or component drawing including numerous components, assemblies, or geometric elements (e.g., points, lines, faces, and primitives), when a large number of components, assemblies, or geometric elements to which dimension lines that are to be excluded from objects to be projected are added exist, a projection drawing to which numerous unnecessary dimension lines are added is created. When such a projection drawing is created, the user currently deals with it by deleting the unnecessary dimension lines. Alternatively, the user deals with it by hiding the dimension lines on the three-dimensional model.
Meanwhile, Japanese Unexamined Patent Application Publication No. 2006-92143 discloses an automatic drawing-generation system. The automatic drawing-generation system includes an attribute-value database in which data regarding attribute values of a project are stored, a three-dimensional model database in which three-dimensional model data of the product are stored; a drawing-frame database in which drawing-frame data for each application are stored; projection-drawing generating means for generating a two-dimensional projection drawing by extracting a specified drawing-frame from the drawing-frame database and projecting a three-dimensional model extracted from the three-dimensional model database on the extracted drawing frame; a dimension database in which data regarding multiple scale-line elements are stored; combining means for extracting scale-line elements corresponding to the shape of the two-dimensional projection drawing from the dimension database, deforming the scale-line elements in accordance with the attribute values of the product, and combining the deformed scale-line elements and the two-dimensional projection drawing; and drawing outputting means for outputting, as a drawing, a two-dimensional projection drawing obtained by the combining of the combining means.
According to the automatic drawing-generation system, during the process in which the three-dimensional model is projected to generate the two-dimensional projection drawing, scale-line elements corresponding to the shape of the two-dimensional projection drawing are extracted from the dimension database and are deformed in accordance with the attribute values of the product, the deformed scale-line elements and the two-dimensional projection drawing are combined, and the drawing is output. Thus, when the projection drawing is automatically generated, only necessary dimension lines can be automatically shown in the two-dimensional space of the projection drawing. This can eliminate work for removing unnecessary dimension lines and adding necessary dimension lines, thus making it possible to achieve laborsaving to some extent in drawing generation. However, the scale-line elements in the dimension database are associated with two-dimensional elements, and thus, any scale element to be used must be added to the dimension database in advance. Thus, there are problems in that work for the processing needs to be done on all scale-line elements and it takes a tremendous amount of work. In other words, since individual drawings are involved in a projection drawing, work for setting a dimension line for each drawing and work involved in the modification become great burdens on the user.